JP3106595B2 - Method for producing composite membrane for reverse osmosis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite membrane used in a reverse osmosis method.

[0002]

2. Description of the Related Art Conventionally, as a membrane for a reverse osmosis method, a composite membrane having a polyamide as an active layer is most often used because of its high water permeability. For example, U.S. Pat.
7, 344, a composite membrane having a crosslinked aromatic polyamide as an active layer, and JP-T-56-500062.
And a composite membrane having a crosslinked polymer containing piperazine units as an active layer. The production method of these composite membranes is that, after an aqueous solution containing a polyfunctional amino compound is applied to a porous polysulfone support membrane, 1,1,2-trichloro-1,2,2-containing polyfunctional acyl halide is applied.
Contacting a trifluoroethane solution. Here, the polysulfone formula _{-Ph-C (CH 3) 2} -Ph-O-Ph-SO 2 -Ph-O- ( where Ph represents. A phenylene group) organic polymer having a repeating unit represented by the -, And the porous polysulfone support membrane is manufactured by the U.S. Department of the Interior, Saltwater Bureau, Research and Development Report No. 35
9 is produced. 1,1,2-Trichloro- used in the production of these composite membranes
It has been pointed out that 1,2,2-trifluoroethane is highly destructive to the ozone layer in the stratosphere and has an adverse effect on the global environment. The United Nations Environment Program (UNEP) has established the Vienna Convention for the Protection of the Ozone Layer. (Adopted in March 1985, 19
Montréal Protocol on Substances That Deplete the Ozone Layer (adopted September 1987, 198)
The use was regulated by
It will be totally abolished in the year. 1,1,2-trichloro-1,2,
Practical membrane performance can be obtained by using aliphatic hydrocarbons such as hexane that does not destroy the ozone layer in place of 2-trifluoroethane. However, these hydrocarbons are flammable and are not suitable for production on an industrial scale. Exaggerated equipment such as explosion-proof equipment is required, and its practicality is low.

[0003]

2,2-dichloro-1,1,1-trifluoroethane is a nonflammable film forming solvent having a small ozone layer destruction coefficient, but porous polysulfone is used as a supporting film. With the crosslinked polyamide-based composite film described above, only low performance can be obtained.

[0004] The present inventors have polyethylene (the Ph here represents a phenylene group.) Earlier as porous support membrane formula -Ph-SO ₂ -Ph-O- having a repeating unit represented by - consisting Terusuruhon As a porous support membrane and a membrane-forming solvent, 2,2-dichloro-1,
By using 1,1-trifluoroethane, it was found that a composite membrane having an active layer of a crosslinked polyamide having high performance was obtained, but the water permeability of the composite membrane was low for practical use.

[0005]

To solve the above-mentioned problems, the present invention has the following arrangement.

On a porous support membrane composed of polyethersulfone having a repeating unit represented by the formula -Ph-SO ₂ -Ph-O- (where Ph represents a phenylene group) In a method for producing a composite membrane for reverse osmosis having an active layer of a crosslinked polyamide obtained by polycondensation of a polyfunctional amine and a polyfunctional acyl halide, 2,2-dichloro-1, Using 1,1-trifluoroethane, after forming the active layer, the composite film was 75 to 9
A method for producing a composite membrane for a reverse osmosis method, comprising performing hydrothermal treatment in a temperature range of 5 ° C.

[0007] In the present invention, the porous polyethersulfone support membrane is the same as the porous polysulfone support membrane, and is similar to the porous polysulfone support membrane in Research and Development Report No. of the U.S. Department of the Interior, Saltwater Bureau. 359.

[0008] The method of adjusting the stock solution is performed as follows. The polyethersulfone is mixed with the aprotic polar organic solvent and heated to 80-95 ° C to completely dissolve. After cooling to room temperature, the film is formed.

When a reverse osmosis membrane as in the present invention is put to practical use, various use forms generally called elements or modules are used to increase the packing area of the membrane per fixed volume so as to increase the processing capacity. Can be For example,
Tubular type that applies a membrane to the inner or outer wall of a thin porous tube, flat type that uses a membrane by supporting and stacking it with a porous plate, spiral type that uses a spirally wound membrane, and thin-walled membrane Although there is a hollow fiber type or the like in which a hollow fiber is used, in the case of the present invention, a spiral type is preferred.

The composite membrane of the present invention has low mechanical strength, and as it is, receives a high tension and a high pressure when the composite membrane is used in a composite membrane production process such as a continuous membrane production method which is a production method on an industrial scale. Can not withstand,
Deforms or destroys and loses its original function. In order to solve such problems, it is used as a so-called fiber-reinforced composite membrane in which a composite membrane is formed on a woven or nonwoven fabric made of fibers. In the fiber-reinforced composite membrane, first, a fiber-reinforced porous support membrane is formed, and an active layer is formed on the fiber-reinforced porous support membrane.

[0011] The fiber-reinforced porous support membrane is formed by wet membrane formation. That is, it is produced by casting a stock solution on a woven or nonwoven fabric and then coagulating (gelling) in a medium (coagulation bath) consisting essentially of water. In this coagulation step, the solvent dissolves in the coagulation bath and is removed from the film. If this is not sufficient, a washing step is provided to remove the solvent. The concentration of polyethersulfone in the stock solution is preferably 14 to 20% by weight. Below this range, the performance exclusion rate of the composite membrane is low, and above this range, the water permeability is low.

In the present invention, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, 2-pyrrolidone, hexamide, etc. are used as the aprotic polar organic solvent used as a stock solution for forming a porous polyethersulfone support membrane. There are methylphosphoric triamide and the like, and dimethylformamide is preferred.

In the present invention, polyfunctional amines include those which react with polyfunctional acyl halides to form a polymer having a crosslinked structure. For example, aliphatic amines include N, N-dimethylethylenediamine , N, N-dimethylpropanediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 1,3-bis (4
-Piperidyl) methane, 1,3-bis (4-piperidyl) propane and the like. The aromatic amine is preferably a diamine or a triamine, and is preferably an aromatic diamine or an aromatic triamine alone.
Alternatively, it is preferably used in the form of a mixture of an aromatic diamine and an aromatic triamine. Examples of the aromatic diamine include m-phenylenediamine and p-phenylenediamine, and m-phenylenediamine is preferred because a crosslinked polyamide ultrathin film having excellent water permeability can be formed. As the aromatic triamine, 1,3,5-triaminobenzene is preferred from the viewpoints of high desalting rate, rejection rate of organic substances, and structural stability of the ultra-thin film layer due to high crosslinking density.

In the present invention, the polyfunctional acyl halide includes those which react with a polyfunctional amine to form a polymer having a cross-linked structure. Examples thereof include trimesic acid halide, benzophenone tetracarboxylic acid halide, and trimellit. Acid halide, pyromellitic acid halide, isophthalic acid halide, terephthalic acid halide, naphthalenedicarboxylic acid halide, diphenyldicarbic acid halide,
Pyridine dicarboxylic acid halide, 1,3,5-cyclohexanetricarboxylic acid halide, 1,3-cyclohexanedicarboxylic acid halide, 1,4-cyclohexanedicarboxylic acid halide and the like can be used. These polyfunctional acyl halides can be used alone or as a mixture. In consideration of the reactivity with the polyfunctional amine, the polyfunctional acyl halide is preferably a polyfunctional acyl chloride.

Next, a method for forming an active layer will be described.

In the present invention, the crosslinked polyamide active layer comprises an aqueous solution containing the above-mentioned polyfunctional amine and a 2,2-dichloro-1,2 containing polyfunctional acyl halide.
A 1,1-trifluoroethane solution is formed on a porous polyethersulfone support membrane by an interfacial polycondensation reaction, which first coats the support membrane with a polyfunctional amine.

The concentration of the amino compound in the aqueous polyfunctional amine solution is 0.1 to 10% by weight, preferably 0.5 to 1% by weight.
0% by weight, and the aqueous solution may contain a surfactant, an organic solvent, an antioxidant, and the like as long as the aqueous solution does not inhibit the interfacial polycondensation reaction.

The aqueous solution of the amine may be coated on the support film as long as the aqueous solution is uniformly and continuously coated on the surface, and a known coating means, for example, coating the aqueous solution on the surface of the support film. It can be performed by a method, a method of immersing the support membrane in the aqueous solution, or the like.

Next, the excessively applied aqueous solution of the amine is removed by a draining step. As a method of draining, for example, there is a method in which the surface of the support film is held vertically and allowed to flow naturally. Next, the 2,2-dichloro-1,1,1-trifluoroethane solution of the above-mentioned polyfunctional acyl halide is brought into contact with the surface of the support membrane coated with the aqueous solution of the polyfunctional amine. The concentration of the polyfunctional acyl halide in the 2,2-dichloro-1,1,1-trifluoroethane solution is usually
The content is 0.01 to 10% by weight, preferably 0.05 to 0.5% by weight.
Above this range, the water permeability is low, and the support membrane may be damaged, resulting in a very low membrane performance of the composite membrane.

The method for bringing the polyfunctional acyl halide into contact with the aqueous solution of the amino compound is carried out in the same manner as the method for coating the support film with the aqueous solution of the amino compound. Thereafter, the substrate is washed with an aqueous alkali solution such as sodium carbonate to remove excessively attached polyfunctional acyl halide.

Next, the obtained composite membrane is subjected to a hot water treatment in a temperature range of 75 to 95 ° C., more preferably in a temperature range of 85 to 95 ° C. The medium in the hot water treatment bath is preferably pure water,
Surfactants and the like may be included as long as they do not adversely affect the film performance. The hot water treatment time is not particularly limited,
A sufficient effect can be obtained in 2 to 5 minutes.

The composite membrane thus obtained exhibits sufficiently good separation performance by itself, but the composite membrane is further immersed in a chlorine-containing aqueous solution having a pH of 6 to 13 to separate the separation membrane, particularly the exclusion rate. In addition, the water permeation speed can be improved. Representative examples of the chlorine generating reagent include chlorine gas, salami powder, sodium hypochlorite, chlorine dioxide, chloramine B, chloramine T, halazones, dichlorodimethylhydantoin, chlorinated isocyanuric acid and salts thereof. Preferably, the concentration is determined by the strength of the oxidizing power. Among the above chlorine generating reagents, an aqueous solution of sodium hypochlorite is preferable from the viewpoint of handleability. There is an important relationship between the oxidizing power and the pH of a chlorine-containing aqueous solution. When the pH is lower than 6, the oxidizing power does not show sufficient oxidizing power, and when the pH exceeds 13, hydrolysis of the amide bond occurs. Both are unsuitable because the ultrathin layer is damaged. Therefore, it is preferable to immerse in a chlorine-containing aqueous solution at pH 6 to 13.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

In the examples, the rejection was determined by the following equation.

Exclusion rate [%] = (1−Solute concentration in membrane permeate / Solute concentration in membrane feed solution) × 100 Example 1 Polyethersulfone (Victre manufactured by IC Corporation)
x 4800) in dimethylformamide (hereinafter D)
Abbreviated as MF. ) And stirred at 90 ° C. for 60 minutes to completely dissolve. The film-forming stock solution obtained in this manner is taffeta (polyester yarn of 150 denier for both warp and weft yarns, weaving density 90 warps / inch, weft 6 inch) made of polyester fiber having a length of 30 cm and a width of 20 cm.
7 / inch, 160 μm thick) was fixed on a glass plate, cast at a thickness of 200 μm at room temperature (20 ° C.), immediately immersed in pure water and left for 5 minutes to obtain a fiber-reinforced polyethersulfone. A support film (hereinafter abbreviated as FR-PES support film) was produced.

The FR-PES support membrane was prepared by adding 1% by weight of 1,3,3
It was immersed in an aqueous solution containing 5-triaminobenzene and 1% by weight of m-phenylenediamine for 1 minute. The support film was slowly pulled up in the vertical direction to remove an excess aqueous solution from the surface of the support film, and then a 2,2-dichloroform containing 0.05% by weight of terephthalic acid chloride and 0.05% by weight of trimesic acid chloride. -1,1,1-trifluoroethane solution is applied so that the surface of the support film is completely wetted,
Let stand for minutes. Next, the support film was set vertically and the excess solution was drained and removed, and then immersed in a 0.2% by weight aqueous solution of sodium carbonate for 5 minutes. After washing with water for 10 minutes, the composite membrane was placed in 90 ° C. pure water and treated for 2 minutes.

The membrane obtained in this manner was adjusted to pH 6.5 with 1500 ppm saline as raw water, and 15 kg / c
As a result of a reverse osmosis test under the conditions of m ² and 25 ° C., the membrane performance was 99.5%, and the membrane performance was 1.10 m ³ / m ² · day.

Comparative Example 1 A composite membrane was prepared in the same manner as in Example 1 except that the hot water treatment was not performed. As a result, the rejection was 99.5% and the water permeability was 0.66.
The membrane performance was m ³ / m ² · day.

Example 2 The FR-PES support membrane of Example 1 was replaced with 4% by weight of 1,3,5
-Immersed in an aqueous solution containing triaminobenzene for 1 minute. After slowly pulling up the support film in the vertical direction and removing excess aqueous solution from the support surface, a dichlorotrifluoroethane solution containing 0.1% by weight of isophthalic acid chloride was applied so that the surface was completely wetted. For 1 minute. Next, the support was placed vertically and the excess solution was drained and removed, and then immersed in a 0.2% by weight aqueous solution of sodium carbonate for 5 minutes. After washing with water for 10 minutes, the composite membrane was heated to 90 ° C.
In pure water for 2 minutes. The obtained film was prepared in Example 1.
As a result of a reverse osmosis test under the following conditions, the membrane performance was 99.2% and the water permeability was 1.04 m ³ / m ² · day.

Comparative Example 2 Example 2 was repeated except that the composite membrane was not subjected to the hot water treatment. As a result, the rejection was 99.1% and the water permeability was 0.63 m.
The membrane performance was ³ / m ² · day.

Example 3 The FR-PES support membrane of Example 1 was replaced with 2% by weight of 1,3,5
-Immersed in an aqueous solution containing triaminobenzene and 2% by weight of m-phenylenediamine for 1 minute. The support film is slowly pulled up in the vertical direction to remove an excess aqueous solution from the surface of the support film, and then to a 2,2-dichloroform containing 0.1% by weight of terephthalic acid chloride and 0.1% by weight of trimesic acid chloride. The -1,1,1-trifluoroethane solution was applied so that the surface of the support film was completely wetted, and allowed to stand for 1 minute. Next, the support film was set vertically and the excess solution was drained and removed, and then immersed in a 0.2% by weight aqueous solution of sodium carbonate for 5 minutes. After washing with water for 10 minutes, the composite membrane was heated to 90 ° C.
In pure water for 2 minutes.

The thus obtained membrane was adjusted to pH 6.5, using 3.5% saline as a raw water, and containing 56 kg / cm ² ,
As a result of a reverse osmosis test at 25 ° C., an exclusion rate of 99.
The membrane performance was 5% and the water permeability was 0.65 m ³ / m ² · day.

Comparative Example 3 The same operation as in Example 3 was carried out except that the composite membrane was not subjected to the hot water treatment. As a result, the rejection was 99.3% and the water permeability was 0.41 m.
The membrane performance was ³ / m ² · day.

[0034]

According to the present invention, a composite membrane for reverse osmosis having a high exclusion rate and a high water permeation rate can be obtained by using a membrane forming solvent having a small ozone layer destruction coefficient.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 71/82

Claims (1)

(57) [Claims] 1. A formula -Ph-SO ₂ -Ph-O- (where Ph represents a phenylene group.) Polyether having a repeating unit represented by - Terusuruhon More comprised porous support film, multi In a method for producing a composite membrane for a reverse osmosis method having an active layer of a cross-linked polyamide obtained by polycondensing a functional amine and a polyfunctional acyl halide, 2,2-dichloro-1,1,1 Using trifluoroethane, after forming the active layer,
A method for producing a composite membrane for a reverse osmosis method, comprising performing hydrothermal treatment in a temperature range of 5 ° C.